1. Field of the Invention
The present invention relates to an apparatus for stacking signatures; more particularly, the present invention relates to a vertical signature stacking system.
2. Description of Related Art
There is disclosed in the art a wide variety of horizontal and vertical stacking machines. These machines are designed to stack sheets of paper, including "signatures". Typically, the signatures have a major plane and a perimeter and are stacked with the major planes of adjacent signatures in contact with the signature perimeters aligned. The signatures are usually rectangular shaped as they are fed from a printer or folding machine. Signatures are fed at a high rate of speed to the stacker, by a conveyor belt assembly.
Horizontal stackers stack the signatures with each individual signature in a vertical position supported on an edge. The stack has a stack axis which is horizontal. Vertical stackers have a vertical stacking support which supports the major plane of the signatures. The term "vertical" is nominal, and used to indicate that the stack is formed with the stack axis vertical or at an angle to the horizontal, typically greater than 45.degree. and most commonly at 45.degree. to 75.degree..
Useful horizontal stackers are disclosed in U.S. Pat. Nos. 4,723,883; 4,670,535; 4,245,832 and 3,378,258. Vertical stackers are also widely known and disclosed in U.S. Pat. Nos. 4,311,090; 4,372,201; 4,678,387; and 4,541,763. Stackers of interest are also disclosed in U.S. Pat. Nos. 4,398,455; 4,397,229; and 4,772,002.
Vertical stackers comprise a vertical stacking table having a vertical support wall. The vertical signature support wall extends from a feed end to a discharge end. The vertical signature support is nominally vertical, but typically at an angle of from 1.degree. to 45.degree. to the vertical. In this way the forming stack rests against the vertical support wall. The vertical stacking table has a sliding signature support fork which can translate up and down along the vertical support wall. The signature support fork can be transverse to and extend from the vertical support track. A stack is squared between the sliding signature support fork and the vertical signature support wall. There can be a feed fork assembly which supports the oncoming signatures as the stack begins to form. The forming stack is transferred from the feed fork to the primary fork. The formed stack on the primary support fork is removed to a bundling and strapping apparatus where the stack is compressed and strapped to form a bundle.
In forming the bundles it is desirable to have end boards or end plates at either longitudinal end of the stack. Apparatus to automatically insert end boards during the stacking operation are disclosed in U.S. Pat. Nos. 4,372,201; 4,311,090; and 4,554,867. Yet another approach is presented in U.S. Pat. No. 4,772,003. The state of the art has been such that the end boards are carefully fit at the ends of the stack. This is because of the rapidly moving and growing stack of signatures.